This invention relates to tube-in-shell heat exchangers.
It relates in particular to expedients to be provided for achieving a greater integrity of joint between the tubes of the heat exchanger and each tube plate (also known as tube sheets) which, with the casing of the heat exchanger, provides the shell through which fluid for contact with the exterior of the heat exchanger tubes is conducted, the other fluid for heat exchange being caused to flow through the tubes. This type of heat exchanger has many applications, one of which is as a steam generator for a fast nuclear reactor cooled by liquid metal, the liquid metal in this case being the fluid in the shell, and the water/steam being the fluid within the tubes.
In the particular application referred to, there have been problems concerned with the integrity of the joint between the heat exchanger tubes and the tube plate. The problems are compounded by the fact that in the said application, for a typical design of plant for a large power station, there are likely to be hundreds of tube to tube plate joints for every steam generator, and if one of the joints should leak, the reactor will have to be shut down so that the leaking joint can be isolated by blocking off or sleeving the offending tube, this being necessary to avoid the consequences of a water/liquid metal chemical reaction. One of the expedients previously proposed (see British Patent No 785,862) for increased integrity is to arrange a gas space between the liquid metal in the shell and the interior surface of the tube plates closing the shell, thereby avoiding welds between the tubes and the relevant tube plate being immersed in hot liquid metal.